Carlsen sacrifices the d3-pawn with check $1 One way to set this up would be to get the king to b2 first.
17... b8a7  18. c1b1 When in doubt, play Kb1 after castling queenside. You can never be too wrong when playing that move. 18... d4c3  19. b2c3  19... a7b6 A calm move, improving the bishop's position. Definitely not an easy move to play,